1. Field of the Invention
The present invention relates to organic compounds and benzoxazole derivatives. Further, the present invention relates to light-emitting elements, light-emitting devices and electronic devices using the benzoxazole derivatives.
2. Description of the Related Art
An organic compound can take a wider variety of structures compared with an inorganic compound, and it is possible to synthesize a material having various functions by appropriate molecular-design of an organic compound. Owing to these advantages, photo electronics and electronics which use a functional organic material have been attracting attention in recent years.
For example, a solar cell, a light-emitting element, an organic transistor, and the like are exemplified as electronic devices utilizing an organic compound as a functional material. These are devices taking advantage of electric properties and optical properties of the organic compound. Among them, in particular, a light-emitting element has been making remarkable development.
It is considered that the light emission mechanism of a light-emitting element is as follows: when a voltage is applied between a pair of electrodes that interpose a light-emitting layer, electrons injected from a cathode and holes injected from an anode are recombined in an emission center of the light-emitting layer to form a molecular exciton, and energy is released to emit light when the molecular exciton relaxes to the ground state. An excited singlet state and an excited triplet state are known as excited states, and it is believed that light can be emitted through either state.
In an attempt to improve element characteristics, there are many problems which depend on a material used, and in order to solve these problems, improvement of element structure, development of a material, and the like have been carried out.
For example, as a material with an electron-transporting property for a light-emitting element, tris(8-quinolinolato)aluminum(III) (abbreviation: Alq) is widely used (e.g., Non-Patent Document 1). However, in the case of using Alq for a light-emitting element, there is a problem in that driving voltage is high. In particular, in view of commercialization, less power consumption is an important issue, and various researches and developments for a material and a light-emitting element with more superior characteristics have been carried out.
[Non-Patent Document 1]
    Taishi TSUJI et al., SID 04 DIGEST, 35, PP. 900-903 (2004)